Is Calhoun County, IA a radon risk area?

EPA's own radon map rates Calhoun County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. That puts Calhoun County in the 75th percentile nationally for radon potential — higher than 75% of the counties EPA has rated.

How Calhoun County compares

About 9,711 people live in Calhoun County, Iowa, spread over 569.846 square miles. Population density there runs about 17 people per square mile. Rank 773 by population within its EPA zone puts Calhoun County at the 27th percentile among zone peers. EPA's geology-based Region 7 groups Calhoun County with 411 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Calhoun County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. EPA's guidance doesn't change because of a Zone 1 label: test the house. What changes is the reason to not put it off in Calhoun County specifically.

Next steps for a home in Calhoun County

Nothing about Calhoun County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find Iowa's state radon program

Calhoun County's test kit answers today; a Airthings radon monitor keeps answering for Calhoun County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.

More on how this number was built

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. Whatever zone Calhoun County carries, the zone explainer covers what it does and doesn't tell you about any one house.